Most of the points have been covered, but I'll throw in my $.02 anyway.
For a 4" lift, you can buy all the parts to do it right and install it yourself without any major modifications for under $400. Plus, you can keep the ride and handling pretty close, if not better (compared to worn out factory components), than stock. The 4"-6" range is also about the right amount of lift if you want to keep somewhat reasonably priced and streetable radial tires (33"-36" range). An 10" lift, for example, would require additional modifications to "do it right" including more steering correction and addressing the driveshaft angle issues, which this would be on top on the higher price for the taller lift. The ride is typically much rougher and the center of gravity requires more caution during normal driving. Then you have the additional costs of the expensive 38" plus tires that usually ride, wear, and handle poorly (in comparison to smaller radial). Then the re-gearing the axles and possibly beefing them up if you ever actually want to use the truck.
I'm not saying you shouldn't lift a truck high if that's what you like, I'm just stating my opinions on why I wouldn't. Also, look around your area.....I bet you don't see too many people driving trucks with 10+ inches of lift and 40" tires everyday to work, there's a reason for it. I've personally know several people who went out and got "big" trucks as daily drivers and all of them either sold them, got another vehicle to drive, or put smaller tires and such on them within a year because they just couldn't take it on a regular basis.
